1. Field
This disclosure is concerned generally with prosthetic devices and specifically with an artificial skeletal ligament.
2. Prior Art
A ligament is a tough band of tissue serving to connect the articular extremities of bones or to support an organ in place. Since skeletal ligaments flexibly stabilize joints, they must withstand considerable amounts of force. Frequently, the skeletal ligaments are subjected to enough force to be torn or otherwise damaged, thereby resulting in instability of the joint. This results in pain and possible damage to other tissues. Although some torn ligaments can be repaired by simply sewing the torn ends together, such repair is not always possible in cases of severe damage or disease. Further, surgical repair is not always predictable and requires a healing period of minimal stress before the ligament can be functionally useful.
The above circumstances have led to the development of a variety of artificial ligaments. Examples of such ligaments can be seen in U.S. Pat. No. 3,988,783 (Collateral Ligament) and U.S. Pat. No. 3,953,896 (Cruciate Ligament), both issued to Treace. Other examples of related prostheses include U.S. Pat. No. 3,973,277 (Bone Implant) to Semple et al, U.S. Pat. No. 3,805,300 (Tendon Prosthesis) to Tascon-Alonso et al, U.S. Pat. No. 3,613,120 (Tendon) to McFarland, U.S. Pat. No. 3,545,008 (Tendon) to Bader, and U.S. Pat. No. 3,842,441 (Tendon Implant) to Kaiser.
Although prosthetic ligaments have a variety of outward appearances, they commonly consist of a flexible longitudinal material having two end portions. The end portions are used to firmly attach the ligament to two adjoining bones such as, for example, the lower femur and the upper tibia. In use, the flexible central portion of the prosthetic ligament is subjected to repeated flexing, stress, and, in some cases, abrasion against bone edges. This can result in deterioration and possible rupture of the prosthesis. Although it has been disclosed that damage due to bone abrasion can be minimized or eliminated by passing the ligament through a flared stainless steel bushing-like device cemented into a bone opening (e.g. U.S. Pat. No. 3,953,896), such devices tend to serve as ligament guides rather than as means for assisting in ligament attachment. Further, the stainless steel bushings that have been disclosed are very hard and do not provide an energy sink for the stresses of a flexing ligament. Without some sort of an energy sink at the points where a flexing ligament contacts a solid body, the possibility of damage due to built up stresses within the flexing ligament is thought to be increased.
We have made a prosthetic ligament which offers advantages over existing ligaments by uniquely combining a means for enhancing ligament attachment within a bone with means for providing an energy sink to minimize the possibility of damage from repeated flexing and abrasion. Details of our findings are disclosed herein.